Ireland’s Regional Modelling System – Development of a New National Car Ownership Model

Ireland’s Regional Modelling System – Development of a New National Car Ownership Model


Barry Colleary, National Transport Authority, David Siddle, Jacobs, David Connolly, Systra


A description of the car ownership and competition components of Ireland's Regional Modelling System


The National Transport Authority (NTA) has a national transport planning remit with responsibilities which include strategic transport planning and the provision of public transport infrastructure and the regulation of PT services. Jacobs and Systra were commissioned in 2012 to support the NTA in developing and enhancing its transport modelling capabilities. The aim of the commission was to create a “state of the art”, robust and transparent regional modelling system that could be implemented at an appropriate scale for each of the five city regions within the NTA’s remit.
The NTA’s new Regional Modelling System (RMS) was complete in 2016 and is comprised of five large regional models, linked by a National Demand Forecasting Model (NDFM). One of the key outputs from the NDFM is the level of car ownership (and therefore car competition) within each Census small area, as this variable is a significant determinant of both trip rate and modal choice. The previous car ownership model used by the NTA was empirically-based and was unable to capture emerging trends such as the recent decline in car ownership amongst younger generations.
This paper explores the different types of car ownership model in use today and their applicability to the RMS. It then describes the process required to develop two new models for the RMS: a car ownership model which can determine the average level of car ownership nationally, based on behavioural trends of individual cohorts; and a car competition model which determines the number of households within each Census Small Area who own at least one car, and how many of those households will have fewer cars than adults. The paper will demonstrate that the new models are a good predictor of car ownership and car competition, but will also highlight weaknesses within the model and recommendations for measures which will improve the model in future.


Association for European Transport